Inertial sensors are utilized in a variety of applications for detecting and measuring inertial motion in one or more dimensions. In the design of navigational and communications systems, for example, such devices are useful in sensing slight variations in linear and rotational motion of an object traveling through space. In automotive systems, such devices can be used to sense tire rotation in antilock braking systems (ABS), and to detect the presence of a collision in airbag deployment systems. Typically, such motion is sensed by detecting and measuring displacement of a resonating structure such as a number of cantilevered beams or interdigitated comb fingers. In an inertial sensor employing a MEMS-type gyroscope and/or accelerometer, for example a number of oscillating proof masses can be used to sense displacement and/or acceleration in response to movement of the device about an input or “rate” axis. In some designs, one or more of the gyroscopes and/or accelerometers can be provided as a part of an inertial measurement unit (IMU) that can be used to measure inertial motion and acceleration in multiple dimensions about an X-axis, Y-axis, and Z-axis.
Packaging of many MEMS devices is typically accomplished using a chip carrier that mounts the MEMS device and associated electronics to an integrated circuit board or other such structure. In the fabrication of MEMS gyroscopes, for example, such chip carriers can be used to package the various drive and sense components of the gyroscope as well as any associated drive and/or sensing circuitry. The particular structure of the chip carrier may vary depending on the type of mechanical and/or electrical connection made between the chip carrier and the other components. Other factors such as heat dissipation, hermeticity, temperature, humidity, chemicals, electromagnetic fields, and/or the existence of mechanical stresses may also play an important role in the type of chip carrier utilized. Accordingly, much effort in the field has focused on providing adequate packaging safeguards to prevent corrosion and/or interference caused by such environmental conditions.
In certain applications, it may be desirable to employ multiple inertial sensors to detect and measure motion of an object in more than one dimension. To accomplish this task, many prior-art devices utilize a cluster of individual packages each containing a single inertial sensor that measures motion about a particular axis or in a particular plane. Such a grouping of inertial sensors may be called an IMU. The use of multiple packages in this manner can greatly increase the overall size of the IMU, in some cases preventing their use in those applications where space is limited. The use of multiple packages can also increase the number of interconnects and circuitry necessary in the overall structure, increasing the complexity and/or cost of the device.